In regenerative medicine, medical technology has been studied actively in recent years to repair and regenerate target tissue and organ by transplanting stem cells. Stem cells capable of differentiating into mature cells of various tissues or organs have been found so far and studied for their clinical application to cell transplantation.
For example, bone marrow-derived cells or skeletal myoblasts have been found to be capable of differentiating into cardiomyocytes. It has been reported that using these cells, cardiomyocytes regeneration is observed in a short time by cell transplantation to heart tissue. However, such cardiomyocyte regeneration observed by the transplantation of the bone marrow-derived cells or skeletal myoblasts has been shown to be attributed not to cardiomyocytes substantially regenerated by the transplanted cells but to cytokine secretion for myocardial protection induced by paracrine effect.
Moreover, the present inventors have developed a technique of separating and purifying, from heart tissue, pluripotent stem cells having the ability to differentiate into various mature cells including cardiomyocytes (the pamphlet of International Publication No. WO 2006/093276). Such pluripotent stem cells derived from heart tissue have been shown to have the excellent ability to differentiate into cardiomyocytes and be most useful, among previously reported cardiac stem cells, in the treatment of heart disease using cell transplantation.
Nevertheless, however useful donor stem cells used in cell transplantation, these donor stem cells (transplanted cells) mostly die 2 weeks after their single transplantation and are thus grafted insufficiently. As a result, it has been shown that the donor stem cells cannot exert the desired therapeutic effect to a maximum extent. Thus, improvement in the survival of grafted donor stem cells in the recipient host environment has been thought to be important for enhancing the therapeutic effect of cell transplantation.
On the other hand, it has previously been reported that a hydrogel containing a growth factor can improve the survival ratio of grafted donor cells in cell therapy by controlled-release of the growth factor in the cell transplantation site (Japanese Patent Laid-Open No. 2002-145797). However, no reports have been made so far about cell transplantation using, in combination, pluripotent stem cells derived from heart tissue and a hydrogel containing a growth factor.